Liquid separation



Inventor Assignee States Patent Stuart E. Madlung, Jr. Martinez, California Appl. No. 694,947

Filed Jan. 2, 1968 Patented Nov. 24, 1970 Phillips Petroleum Company, a corporation of Delaware LIQUID SEPARATION I l Qialrn, 2 Drawing Figs,

u.s.fl 210/71, 210/73, 210/84; 55/ 5 1111.1 1 801d 17/04 ma ofSearch 210/21, 22, 71-73,s3, 84;55/45,46,48, so, 51,54,55

[56] References Cited UNITED STATES PATENTS l, 6ii,256, 12/1926 Suczek ss/sox 2,307,078 1/1943 Reed 210/21x 2,588,794 3/1952 Barton 210/21 3,217,466 11/1965 Bogart ss/s4x Primary Examiner-John W. Adee AttorneyYoung Quigg ABSTRACT: in a liquid separation system comprising phase separation followed by a vacuum flash of one of the separated components, the vacuum is produced by pumping one of the liquids through an eductor prior to introduction into the phase separation zone.

Patented Nov. 24, 1970 FIG.

FIG. 2

INVENTOR.

S. E. MADLUNG, JR.

A T TORNEVS mourn SEPARATION This invention relates to liquid separation. In one aspect it relates to a method for separating liquids and removing by flash vaporization small quantities of alower boiling liquid entrained in a higher boiling liquid.

Often when two substantially immiscible liquids are separated by phase separation, a verysmallquantity of one is dissolved and/or entrained in the other. In many instances such small quantities are not harmful and can be permitted to remain. However, in other instances, even trace quantities of one of those liquidsmust beremoved from the other. This occurs, for example, when one of the liquids cannot be tolerated 1 in a further chemical reaction occurringwith theother of the liquids, or whenthe one liquid cannot be tolerated'in the disposal of the other. An exampleof the latter occurs inthe operation of oil refineries wherein .hydrocarbon streams are water washed, with, the spent wash solution being dumped continuously to a disposalsystemJThe water sometimes con-. tains sufficient amountsof hydrocarbonto. be wasteful in the.

loss of hydrocarbons and to contribute to water andair pollution problems.

n object of the inventionis to, separate liquids. Another object of the inventionfisto.provide fortheremoval of trace" quantities of one liquid from anotherfollowing a phase separation. Another object of the invention is to operate economically a separationsystem comprisingphase separation followed by a vacuumflash.

Other aspects, objectsland the advantages of the invention are apparent in the written,description,.the drawing and the claims.

According to the inventionthe vacuum for a vacuum flash following a liquid phase separation is provided by-pumping one of the liquids being fed to the phase separation zone to an eductor to withdraw flash vapors from the flash zone. 1n the flash zone small quantities of lower boiling components of one of the liquids are'removed from the phase separated stream comprising the other liquid.The vacuum is provided-by pumping through the eductor either one of the. liquids being'fed to the phase separation zone or a mixture of'the two. The lower boiling liquid or the liquid comprising lower boiling components can be less or more dense than theother liquid stream and, therefore the separated-phase being passed to the flash. 'separationzone can be either the upper or lower of the phases in the phase separation zone.

etc. If desired, the oil can be introduced into pipe 24, thereby utilizing pump 26 for mixing.

in operation, oil containing a small amount of residual aqueous caustic (NaOH) ismixed with water and introduced into tank 11. The water removes substantially all of the caustic from the oil. Although the water and oil are substantially immiscible, a small quantity of oil is dissolved in the'water and a small quantity of water is carried with the oil. The small amount of water leaving with the oil through pipe 34 is not necessarily harmful or wasteful and can be removed. in downstream separation zones if necessary. On the other hand, oil leaving with the water through pipe 22 is highly undesirable, both from. the standpoint of waste of hydrocarbon products and from the standpoint of water and/or air pollution, depending upon the ultimate method of disposaL-Therefore, the water is passed through flash zonel2, where substantially all of the oil is vaporized throughthe addition of heat by the steam coming in through pipe 28 andby the vacuum which is provided by eductor 19, powered by the makeup water en- 'tering through pipe 18. The vapor thus removed is returned to tank "11 andeventually removed through pipe 34, since the tanks 11 and 12 of HG. 1, respectively. However, in this in the drawing ,,FlG.}l is a schematic illustration of one form of separation and flash system.

FIG. 2 is a schematic illustration of a phase separation and flash system wherein the-lowerdensity liquid is the higher boiling.

In the system illustratedv in FIG.v 1,:there are provided a phase separation tank-11 ,'and a flash tank: 12. Oilhavinga water soluble, impurity, for example 'residue from-a caustic wash. enters through pipe 13 and ispassedthrough-pipe I4 I and pipe 16 into tank 11. Make-up water passesthrough pipe; 18, eductor 19, pipe 21; and pipe 16 into tank 11. Water..is-

withdrawn from tank '11 througheductor 23 totank 12, and

through pipe 24,pump 26,pipe 27, pipe 14 and pipe 16 to tank 11. Steam enters through ;pipe.28.intoeductor 23. Vapor is withdrawn from the top of tank. 12 through pipe.2-9.to edu'ctor l9 andis introduced into the waterbeingfed through pipe 21 and pipe 16 to tankl1-1. Wateris removed from the bottom oftank 12 through pipe 3l;'which can be long enough to serve as a water. leg, and throughpipe32 to the sewer. Vent -33'is provided if desiredor necessary. If desired, a pumpcan be provided instead of a water leg. Oilis removed from tank 11 through pipe 34.;A liquidlevel controller 36 adjusts valve 37' to maintain the withdrawalof waterat the desired rate to maintain the level of the-interface in tank. 11 in a desired range. Similarly, liquid level controller 38'controls valve 39 and the withdrawal of water from tank 12 to maintain the" desired water level therein.

If desired, mixing'means 41. is provided. This can be one or more orifices or valves, a conduit having a tortuous flow path,

system,the oil is withdrawn from tank 51 to tank52 from which the lower boiling water is removed through eductor 53 and returned to tank 51. Although eductor S3 is shown as powered by oil entering the system through pipe 54, alternatively itcould be powered by water which is shown as entering through pipe 56. That is to say, the make-up water could be passed through eductor 53 on its way to tank 51. An eductor interface intank 51. With the withdrawal of the oil above the interface, it will be seen that this controller decreases the flow of water through. valve 66 in water line 67 as the interface lowers-increases the. flow as the interface rises above the desired level.

. Heat can be provided if desired by indirectly heating line 58, or line -68,through which oil flows to tank 52, or by other means.

Oil which is substantially completely water-free is recovered as product by way of line 60;

In an example according to the invention, in a system as illustrated in FIG.- 1, vesselll is operated at a pressure of 180 p.s.i.a. and a temperature of F. and vessel 12 at 8 p.s.i.a. and F. Make-up water enters through pipes 17 and 18 at 400 p.s.i.a. and 80F. at a rate of barrels per hour. Steam enters through pipe 28 at 40 p.s.i.a. and 267F. at the rate of 3,000 pounds per hour. The hydrocarbon feed brought in throughpipe 13 is an alkylate yield from a sulfuric acid alkyla- 'tion unit, which alkylate yield has been neutralized with caustic. The specific gravity of this alkylate yield at 60F. is 0.6. The boiling rangeis 43 to 400F.'and it contains a trace of aqueous caustic (NaOHisolution. The stream enters at a rate-of 1,700barrels per hour. The hydrocarbon product is removed through pipe34 and passed to a deisobutanizer for further processing. The table presents a material balance on the materials at various points in the system, the numbers at training t am th rein and then introducing said water the heads ofthe columns referring to types of FIG. 1. phase ing steam into a reduced pr zone;

TABLE Caustic- Used washed wash Make-up Flashed Flashed Recycle alkylate Washed Recycle Stream component Steam water water vapors residue to washer feed alkylate wash 28 22 18 29 13 34 i 24 B/H, hydrocarbon 0.20 0.2 Nil 0.2 1,700 1700 0.76. 40 lbs. steam, pounds/hr.. 3,000 n Water, as indicated 150 BILL 150 B/H 1.67 #/hr 158.6 13/11 150 B/H Caustic solution Trace Trace Trace I As va or.

b Inclu es steam condensate (1.67 #/hr.=0.00475 B/hr.). 3,000 lbs. steam make 8,57 bbl. H2O liquid.

d Includes 1.67 #lhr. water vapor as condensate.

= Containing trace water in solution.

NOTE.B/H=barrelslhour; #/hr.= pounds/hour.

Reasonable variation and modification are possible within e. vaporizing said small quantity of hydrocarbon in said the scope of the invention which sets forth a system for phase reduced pressure Z0116; separation followed by vacuum flash of one of the separator f. removing from said reduced pressure zone said water components. phase as liquid substantially free of said small quantity of I claim: 25 hydrocarbon but containing said impurity; 1.Amethod of removal of a nonvolatile water soluble impug. pumping make-up water into said separation zone rity from ahydrocarbon comprising the steps of: through a second eductor which produces the reduced a. admixing water and a hydrocarbon containing a nonpr ssur in Said reduced Pressure Zone;

volatile water soluble impurity; h. removing said small quantity of hydrocarbon and at least b. passing the resulting mixture into a phase separation zone a port o of Said Steam from i reduced Pressure Zone wherein are formed a liquid hydrocarbon phase lean in through said second eductor; said impurity and a liquid water phase ontaining id imi. introducing said small quantity of hydrocarbon and said purity and a small quantity of said hydrocarbon; portion of said steam along with said make-up into said 0. removing said water phase from said phase separation p e separation 20116; and

zone; j. recovering from said separation zone said hydrocarbon cl. pumping said water phase through a first eductor and enphase ially free of Said i pu ity. 

